Types of chemical reactions
There are many different types of chemical reaction.
For example, oxidation is the reaction of a substance with
oxygen.
What is the word equation for the oxidation of copper?
copper
+
oxygen
➨
copper oxide
Reduction is the opposite of oxidation. What do you think is
formed in the reduction of magnesium oxide?
magnesium oxide
1 of 40
➨
magnesium
+
oxygen
© Boardworks Ltd 2008
Combustion
A common combustion
reaction is petrol burning
with oxygen in a car engine.
The products of this
reaction are carbon
dioxide and water.
What is the word equation for this combustion reaction?
petrol
+
oxygen
➨
carbon dioxide
+
water
Combustion involves reacting with oxygen, so it can also be
classified as another type of reaction. Which one?
2 of 40
© Boardworks Ltd 2008
What is combustion?
Combustion is the scientific word for burning.
It is the chemical reaction that takes place when a substance
burns and reacts with oxygen to produce heat and light
energy.
3 of 40
© Boardworks Ltd 2008
The fire triangle
4 of 40
© Boardworks Ltd 2008
Putting out fires
If a fire starts accidentally, it is important to be able to put it out
quickly and safely.
To put out a fire, you can
cut off the supply of any
side of the fire triangle.
For example:
l  putting water on burning
wood cuts off the heat.
l  putting sand on burning oil
cuts off the oxygen.
l  cutting down trees in a forest
fire cuts off the supply of fuel.
5 of 40
© Boardworks Ltd 2008
Combustion of methane
Natural gas, methane, is often burned for cooking. Methane is
made up of carbon and hydrogen.
l  What gas does methane burn with? oxygen
l  What substance will the carbon in methane change
into when it burns? carbon dioxide
l  What substance will the hydrogen in methane change
into when it burns? water
l  What is the word equation for the combustion of methane?
methane
6 of 40
+
oxygen
➨
carbon
dioxide
+
water
© Boardworks Ltd 2008
Word equations for combustion
When substances combust, the new substances formed are
called ‘oxides’.
What are the word equations for these combustion reactions?
1. Coal (made from carbon) burns and forms carbon dioxide.
carbon
+
oxygen ➨ carbon dioxide
2. Hydrogen burns and forms dihydrogen oxide (i.e water!).
hydrogen
+
oxygen
➨
water
3. Methane burns and forms carbon dioxide and water.
methane
7 of 40
+
oxygen ➨ carbon dioxide
+
water
© Boardworks Ltd 2008
Symbol equations for combustion
What are the symbol equations for these combustion reactions?
1. Coal (made from carbon) burns and forms carbon dioxide.
+
+
carbon
C
oxygen
➨
carbon dioxide
O2
➨
CO2
2. Hydrogen burns and forms dihydrogen oxide (i.e water!).
hydrogen
2H2
+
+
oxygen
➨
water
O2
➨
2H2O
3. Methane burns and forms carbon dioxide and water.
methane
CH4
8 of 40
+
+
oxygen ➨ carbon dioxide
2O2
➨
CO2
+
+
water
2H2O
© Boardworks Ltd 2008
Complete and incomplete combustion
Fuels like methane, butane
and petrol are hydrocarbons.
Hydrocarbons are compounds
made of carbon and hydrogen.
When these hydrocarbon fuels
burn in a good supply of oxygen,
they burn completely to make
carbon dioxide and water.
If there is a lack of oxygen, incomplete combustion takes
place. This means that the fuel burns to produce water,
carbon monoxide and carbon particles.
9 of 40
© Boardworks Ltd 2008
Incomplete combustion
Incomplete combustion is a hazardous problem because
the products of the process are toxic.
Carbon monoxide prevents people’s
blood from carrying oxygen.
Carbon particles make city
buildings very dirty, and they can
get into people’s lungs and cause
breathing problems.
What precautions do you think
people take in their homes to
prevent incomplete combustion?
10 of 40
© Boardworks Ltd 2008